Umm ‘Umara, daughter of Ka‘b, said that once when the Prophet (ﷺ) visited her and she called for food for him, he told her that she must eat also; but when she replied that she was fasting he said, “When people eat beside one who is fasting the angels invoke blessings on him till they finish eating.” Ahmad, Tirmidhi, Ibn Majah and Darimi transmitted it.
Source: sunnah.com
Other translations
Arabic
وَعَن أم عمَارَة بنت كَعْب إِنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ دَخَلَ عَلَيْهَا فَدَعَتْ لَهُ بِطَعَامٍ فَقَالَ لَهَا: «كُلِي» . فَقَالَتْ: إِنِّي صَائِمَةٌ. فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «إِنَّ الصَّائِمَ إِذَا أُكِلَ عِنْدَهُ صَلَّتْ عَلَيْهِ الْمَلَائِكَةُ حَتَّى يَفْرَغُوا» . رَوَاهُ أَحْمَدُ وَالتِّرْمِذِيّ وَابْن مَاجَه والدارمي
sunnah.com